Filtration method
Provided is a filtration method for the step of removing viruses in a process of producing a protein preparation during which an intermediate protein preparation with a high protein concentration flows at high pressure to a virus removal filter. The filtration method employs a virus removal filter which has a close fitting nozzle of which the inlet at least has a pressure resistance of 600 kPa or more, and an effective area of the virus removal membrane of at least 0.0001 m 2 and no more than 0.03 m 2 . An intermediate protein preparation with the protein concentration raised to at least 20 mg/ml and no more than 100 mg/ml by means of a purification process flows down to said virus removal filter under conditions in which the inlet pressure of the intermediate protein preparation is at least 150 kPa and no more than 600 kPa, the average protein filtration speed is at least 1.0 kg/m 2 /hr, and the filtration time is at least 1 hour and no more than 5 hours, to give an intermediate protein preparation filtrate with a viral removal rate (LRV) of ≧3.
1. A filtration method for filtering an intermediate protein product having a predetermined protein concentration through a virus removal filter at a predetermined pressure, comprising:
(1) using a virus removal filter that comprises a container that has at least one inlet and at least one outlet, and a virus removal membrane that is made of a hydrophilized synthetic polymer for removing viruses from the intermediate protein product, the space inside the container is divided by the virus removal membrane into an inlet-side space and an outlet-side space, at least the inlet of the container has a nozzle having a fitting structure that has a pressure resistance of 600 kPa or more, and the virus removal membrane has an effective membrane area of 0.0001 to 0.03 m 2 ,
(2) subjecting the intermediate protein product, which has a protein concentration of 30 to 100 mg/mL and has been pre-filtered, to dead-end filtration for 4 to 5 hours through the virus removal filter at an inlet pressure of 294 to 600 kPa and an average protein filtration rate of 1.6 kg/m 2 /Hr or more, and
(3) obtaining a filtrate of the intermediate protein product having a virus removal rate (LRV: logarithmic reduction value) of 3 or more.
2. The filtration method according to claim 1 , wherein the virus is selected from Parvoviridae, Retroviridae, Flaviviridae, Reoviridae, Paramyxoviridae, Herpesviridae, Picornaviridae, and Papovaviridae.
3. The filtration method according to claim 1 , wherein the protein in the intermediate protein product is an immunoglobulin.
4. The filtration method according to claim 3 , wherein the immunoglobulin is immunoglobulin G.
5. The filtration method according to claim 1 , wherein the virus removal membrane is a hollow fiber virus removal membrane.
6. The filtration method according to claim 1 , wherein the intermediate protein product was pre-filtered using a filter comprising a cellulose hollow fiber membrane.